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Overview of Mobile File Systems

Overview of Mobile File Systems. Presented by Steve Todd For WSU CS 898T Mobile and Wireless Networks Class 5/3/04. Introduction. Present overview of mobile file systems Present several characteristics that complicate file system operation for mobile applications

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Overview of Mobile File Systems

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  1. Overview of Mobile File Systems Presented by Steve Todd For WSU CS 898T Mobile and Wireless Networks Class 5/3/04

  2. Introduction • Present overview of mobile file systems • Present several characteristics that complicate file system operation for mobile applications • Present overview of Coda - How Coda deals with these complications

  3. Mobile File Systems • Allow mobile users to run applications that access shared files over a mobile network • Applications behave the same regardless of where user is located • Act as middleware between operating system and application

  4. Mobile vs. Stationary • Resources for mobile devices never more than for stationary devices • Mobility inherently hazardous • Mobile device network connectivity highly variable in reliability and performance • Mobile devices dependent on a finite energy source

  5. Autonomy vs. Interdependence • Balance between autonomy and interdependence necessary for optimal system performance • Adaptability = main goal of mobile file systems (compromise)

  6. Mobile File Systems Characteristics • Provide location transparency • Provide replication (optimistic/pessimistic) • Provide cache consistency • Provide connected and disconnected operational modes • Provide scalability

  7. MFS Modes of Operation

  8. Coda Distributed File System • Files grouped into volumes replicated on Coda servers • Version stamping to resolve conflict • Client caching reduces network dependence and provides scalability • Uses optimistic approach • Callbacks to maintain cache coherency

  9. Coda Client File Session

  10. Coda Client States

  11. Conclusions • Data consistency, data caching, scalability, location transparency, data replication, and availability • Adaptability to network

  12. References • Satyanarayanan, M. Fundamental Challenges in Mobile Computing. Fifteenth ACM Symposium on Princ. of Distr. Comp. May 1996. • Honeyman, P., Huston, L. B. Communications and Consistency in Mobile File Systems. IEEE Personal Communications, Dec. 1995, pp. 44-48. • Braam, P. J. The Coda Distributed File System. Carnegie Mellon University. http://www.coda.cs.cmu.edu/ljpaper/lj.html. • Schiller, J. Mobile Communications (2nd ed.). Addison-Wesley, 2003, pp. 375-381. • Tanenbaum, A. S., van Steen, M. Distributed Systems: Principles and Paradigms. Prentice Hall, 2002, pp. 604-623.

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